sequencekeygenerator.java

jGossip是一个简单而功能强大的Java论坛软件（消息板）

/*
 * $Id: SequenceKeyGenerator.java,v 1.2 2004/06/28 01:33:48 alexnet Exp $
 *
 * ***** BEGIN LICENSE BLOCK *****
 * The contents of this file are subject to the Mozilla Public License
 * Version 1.1 (the "License"); you may not use this file except in 
 * compliance with the License. You may obtain a copy of the License 
 * at http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS"
 * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
 * the License for the specific language governing rights and 
 * limitations under the License.
 *
 * The Original Code is JGossip forum code.
 *
 * The Initial Developer of the Original Code is the JResearch, Org. 
 * Portions created by the Initial Developer are Copyright (C) 2004 
 * the Initial Developer. All Rights Reserved. 
 * 
 * Contributor(s): 
 *              Alexey Pavlov <[e-mail]>
 *        
 * ***** END LICENSE BLOCK ***** */
package org.jresearch.gossip.dao.drivers.keygen;
        
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.HashMap;
import java.util.Map;

/**
 * Obtains a key from a sequence table.
 * 
 * @author <a href="[e-mail]">A. Pavlov</a>
 * @version $version$ $Date: 2004/06/28 01:33:48 $
 */
public class SequenceKeyGenerator implements KeyGenerator
{
	static Map sequenceDefs = new HashMap();
	
	static {
		SequenceKeyGenerator.sequenceDefs.put(IKeyGenConst.KEY_NAMES[IKeyGenConst.KEY_MESSAGE][0], "SELECT nextval(JRF_KEY_MESSAGE_SEQ)");
		SequenceKeyGenerator.sequenceDefs.put(IKeyGenConst.KEY_NAMES[IKeyGenConst.KEY_THREAD][0], "SELECT nextval(JRF_KEY_THREAD_SEQ)");
		SequenceKeyGenerator.sequenceDefs.put(IKeyGenConst.KEY_NAMES[IKeyGenConst.KEY_USER][0], "SELECT nextval(JRF_KEY_USER_SEQ)");
		SequenceKeyGenerator.sequenceDefs.put(IKeyGenConst.KEY_NAMES[IKeyGenConst.KEY_WHOIS][0], "SELECT nextval(JRF_KEY_WHOIS_SEQ)");
		SequenceKeyGenerator.sequenceDefs.put(IKeyGenConst.KEY_NAMES[IKeyGenConst.KEY_FORUM][0], "SELECT nextval(JRF_KEY_FORUM_SEQ)");
		SequenceKeyGenerator.sequenceDefs.put(IKeyGenConst.KEY_NAMES[IKeyGenConst.KEY_GROUP][0], "SELECT nextval(JRF_KEY_GROUP_SEQ)");
	}
	
    public boolean isBeforeInsert() { return true; }

    /**
     * Obtains a key from a sequence table.
     *
     * @param classMap provides mapping of class to sql persistence
     * @param db the database for persisting the class described in the 'ClassMap'
     * @return the key
     * @exception PersistenceException if an error occurs
     */
    public Object generateKey(String[] primaryKeyName, Connection conn)
			throws SQLException
    {
		Object identity;
        ResultSet rs = null;;
		Statement stmt = null;
		final String tableName = primaryKeyName[0];

		try {
			// Create SQL statements of the form "SELECT nextval(JRF_KEY_SEQUENCE)"
			String sql = (String)SequenceKeyGenerator.sequenceDefs.get(tableName);
		    stmt = conn.createStatement();
		    rs = stmt.executeQuery(sql);
		    if (rs.next()) {
				identity = rs.getObject(1);
		    }
		    else
	                throw new SQLException("persist.sequenceKeyGenFailed");
		} finally {
		    try {
			if (rs != null)
			    rs.close();
			stmt.close();
		    } catch (SQLException excep) {
		    
		    } finally {
			rs = null;
			stmt = null;
		    }
		}
		return identity;
    }

}